OK, say you went ahead and took civil action against him. Let's look at some of the possible outcomes:
1. He ends the relationship with your wife, but wife wants to continue. She files for D and "waits it out."
2. He ends relationship with your wife, and wife reluctantly sulks back to you.
3. They say the relationship has ended, but instead they take it "underground"
4. He does not end the relationship, and you collect money from him. Oh, and your wife files for D because she wants it to continue, and once the money has changed hands, there's not much more you can do.
Of these scenarios, only #2 has the outcome that you want (I presume you want her to return to you and keep the family intact). But it's a hollow victory, because wife will still have feelings for him, and will not have any inclination to be drawn to you.
I agree with lwb. She has to end it. No court in the world can tear a person away from their (new) "soul mate."
This doesn't mean that you shouldn't take action. The choice is yours. Just be prepared to end up pushing your wife into his arms.
